Cutting inserts such as those described in WO/2011/037186 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2010-69614A (Patent Document 2) are known as cutting inserts used in turning processing. In the cutting insert described in Patent Document 1, a rake surface extending along a cutting edge includes a first region and a second region. A rake angle at the second region is greater than a rake angle at the first region.
The cutting insert described in Patent Document 2 includes a recess defined between a cutting edge (corner cutting edge) at a corner portion of a top surface and a convex portion on the top surface. Due to this sort of recess being provided, chips can be processed even when cutting is performed with extremely low depth of cut using the corner portion.
The region of the corner cutting edge used in the cut processing changes when the depth of cut is changed in the cutting with extremely low depth of cut using the corner portion. Here, because the direction in which the chip advances changes, the optimal rake angle also changes depending on the depth of cut. However, with both the second region of the rake surface described in Patent Document 1 and the front wall portion of the recess described in Patent Document 2, the rake angle with respect to the corresponding cutting edge is constant. Consequently, in cases where the depth of cut changes such as in profiling for example, processing of the chip may become unstable.
In light of the foregoing, an object of an aspect is to provide a cutting insert capable of discharging chips in a stable manner, even when the depth of cut is changed in cutting with depth of cut using a corner portion.